Close Encounters With Jets Show Russia’s Anger at NATO Buildup, U.S. Says

WASHINGTON — When the Pentagon complained about a Russian fighter plane performing a barrel roll near an Air Force reconnaissance plane in international airspace over the Baltic Sea on April 29, a quick response came from Moscow, which claimed that the American plane did not have its transponder turned on.

“The U.S. Air Force has two solutions,” the Russian Defense Ministry said in a sharp statement. “Either not to fly near our borders or to turn the transponder on for identification.” (American officials said the transponder had, indeed, been turned on.)

With that, American officials and foreign policy experts said, Russia delivered its response to President Obama’s decision this year to substantially increase the deployment of heavy weapons, armored vehicles and other equipment to NATO countries in Central and Eastern Europe. The move is meant to deter Russia from further aggression in the region.

By sharply ramping up so-called intercepts of American ships and planes in Central and Eastern Europe, Russia is demonstrating its anger over the increased American military presence in a region it considers part of its backyard, White House officials said. They called the Russian actions harassment.

In just the last month, there have been three incidents.

On April 12, a Russian jet buzzed an American guided missile destroyer, the Donald Cook. A photo released by the Pentagon showed the jet passing over the ship’s bow at an extremely low altitude. Russia accused the United States of sailing the Cook close to Russia’s border in the Baltic and warned that the Russian military would respond to any future incidents.

Even so, Russia appears to be threading a needle. The warplane did not turn on its radar and had no weapons under its wings, showing that it was not in attack mode, officials said. That may have contributed to the decision by the Donald Cook’s commander not to respond.

Two days later, a Russian warplane intercepted an American reconnaissance plane over the Baltic Sea at what American officials said was an unsafe distance, prompting another protest from the Pentagon.

And in the latest incident, on April 29, Pentagon officials insisted that the American plane did turn on its transponder, which identifies the plane for air traffic control.

“Let me make clear that the transponder was on,” said Michael Carpenter, the deputy assistant secretary of defense for Russia, Ukraine and Eurasia, in an interview. “That allegation is false.”

Obama administration officials said they interpreted Russia’s statement as a demand that the United States stay out of the Baltics — and that is not going to happen, these officials said.

“We’re going to continue to fly, and we’re going to continue to operate in the Baltic Sea,” Mr. Carpenter said. “This is not going to change our activities one iota.”

But the game of chance underway in the skies and on the seas of Central and Eastern Europe could lead to miscalculations, American officials warn.

Barrel rolls, for instance, are exactly what they sound like — maneuvers in which the fighter plane makes a complete spin. Doing something like that in proximity of another aircraft thousands of feet up in the sky can be dangerous.

Defense Department officials say they worry that an erratic move at high speed in the air could clip the wing of either aircraft, potentially causing an accident and even death. A midair collision between a Chinese fighter and a Navy surveillance aircraft in international airspace in 2001 was cited as an example.

Few people believe that such a miscalculation would lead to war. But it would certainly exacerbate tensions between Russia and NATO when both sides have been adopting a more aggressive military posture.

As he assumed command of NATO’s military arm on Wednesday in Mons, Belgium, Gen. Curtis M. Scaparrotti said NATO needed to be ready to “fight tonight,” bringing to the European theater a term that has long been used to reflect the readiness of American troops in South Korea.

Such talk has become common as NATO struggles to deal with Russia after Moscow’s military activity in eastern Ukraine. The White House has added more than $3.4 billion for military spending in Europe in 2017, more than quadrupling the current budget of $789 million, on weapons and equipment that will be used by American and NATO forces. Among the countries where the equipment and additional forces will be deployed are Hungary, Romania and the Baltic States, Pentagon officials say.

The United States and its NATO partners are embarking on a series of military exercises in advance of July’s NATO summit meeting in Warsaw, in part to demonstrate strength and resolve. But these exercises are expected to rile Moscow.

In June, as many as 12,000 American troops will join service members from a number of European allies in Poland for an exercise called Anakonda, which planners say will be the largest military exercise in Europe in years. Altogether, 25,000 troops from 24 NATO and partner countries will be involved.

NATO countries are also planning a new round of maritime exercises in the Baltic Sea before the Warsaw summit meeting. And economic sanctions against Russia for aggression in Ukraine are set to roll over in July.

“You add all of this up and it sends a pretty clear message to Moscow,” said Derek Chollet, a former assistant secretary of defense in the Obama administration and the author of the forthcoming book “The Long Game.” “The question will be, how will they react?”

But Russia is reacting, Mr. Chollet and other Russia experts say.

The response from the United States and the West has been to send official complaints to Moscow accusing Russian pilots of unprofessional behavior and raising the specter of miscalculations. But one of President Vladimir V. Putin’s greatest domestic public relations successes has been his ability to position the incidents as a valiant Russia’s defending itself from an aggressive United States and NATO in its own backyard.

“They may look like they’re acting like children in our eyes,” Michael McFaul, a former United States ambassador to Russia, said in an interview Friday. “But not in the eyes of their own citizens.”

In Russia, Mr. McFaul said, “we’re painted as the provocateurs.”

A version of this article appears in print on , on Page A4 of the New York edition with the headline: Close Encounters With Jets Show Russia’s Anger at NATO Buildup, U.S. Says. Order Reprints | Today’s Paper | Subscribe